Sealing and cooling device for a pump shaft



Oct. 26, 1965 s. A. CARSWELL 3,213,798 SEALING AND COOLING DEVICE FOR A PUMP SHAFT Filed March 16, 1964 3 Sheets-Sheet l INVENTOR. F/G. SAMUEL A. CARSWELL ATTORNEY Oct. 26, 1965 s. A. CARSWELL SEALING AND COOLING DEVICE FOR A PUMP SHAFT Filed March 16, 1964 3 Sheets-Sheet 2 Oct. 26, 1965 s. A. CARSWELL 3,

SEALING AND COOLING DEVICE FOR A PUMP SHAFT Filed March 16, 1964 3 Sheets-Sheet 3 3,213,798 SEALING AND COOLING DEVICE FOR A PUMP SHAFT Samuel A. Carswell, Martinsville, N.J., assignor to Ingersoll-Rand Company, New York, N.Y., a corporation of New Jersey Filed Mar. 16, 1964, Ser. No. 352,182 4 Claims. (Cl. 103-111) This invention relates in general to seals for rotary shafts and more in particular to a sealing and cooling arrangement for a shaft of a rotary pump.

For many rotary pump uses, particularly those for boiler feed and boiler circulation requiring pumping of water of high pressure and high temperature, it is important that the fluid being pumped is prevented from leaking out of the pumping or impeller chamber along the shaft and into the adjacent seal chamber for the shaft of the pump. This causes overheating of the shaft and associated components, or, when leaking along the shaft to atmosphere, causes the water to flash into steam.

In present type boiler circulating pumps in which a commonly known sealing arrangement in the seal chamber of the pump is used, such as shown in FIGURE 1 but without the auxiliary impeller, injection water at low temperature and at a pressure higher than the circulating pump pressure is usually taken from the boiler feed pump and introduced into the stufling box or seal chamber formed in the pump casing. The injection water is conducted to flow along the shaft into the pumping or impeller chamber of the pump for purposes of cooling the shaft and preventing the high temperature water present in the impeller chamber of the pump to leak therefrom along the shaft and into the adjacent seal chamber. However, under certain conditions, and in particular at low boiler loads when the boiler feed pump operates at variable speeds, the pressure of the injection water decreases to equal to or even lower than the suction pressure of the circulating pump. This results in either stagnation of the injection water in the seal chamber of the pump casing, or back flow of the high temperature high pressure water from the impeller chamber along the shaft and into the seal chamber causing overheating of the the shaft and flashing of the water into steam when the water leaks off to atmosphere.

In order to avoid these objectionable results, the pump is provided with an auxiliary impeller and auxiliary impeller housing positioned adjacent the main impeller chamber to create a constant pressure drop at the eye of the auxiliary impeller relative to the pressure of the injection fluid. In this manner the injection fluid flows constantly to the auxiliary impeller from where it is pumped into the main impeller chamber independent of the pressure of the injection fluid, thereby insuring prevention of escape of the high pressure high temperature water from the main impeller chamber along the pump shaft and into the seal chamber.

According to the invention, the pump includes an impeller chamber and a seal chamber through which the pump shaft extends. In the seal chamber is provided a sealing means adapted to permit a limited flow of cooling fluid introduced into the seal chamber to flow through the clearance between the sealing means and the shaft, and, an auxiliary impeller mounted on the pump shaft to rotate therewith to cause the cooling fluid to flow constantly along the shaft from the seal chamber into the impeller chamber to prevent the fluid in the impeller chamber to flow therefrom into the seal chamber.

An object of this invention is to provide an effective cooling and sealing arrangement for the shaft of a boiler feed pump.

Patent Another object of this invention is to provide a simple and reliable cooling and sealing arrangement for the shaft of a boiler feed pump.

Yet another object of this invention is to provide for increased pump life and pump efliciency.

Other objects and advantages of the invention will be apparent from the following description taken in con junction with the accompanying drawings wherein like reference numerals refer to [like parts, and in which:

FIGURE 1 is a longitudinal section through a part of a centrifugal pump showing the preferred embodiment of the invention,

FIG. 2 is an enlarged sectional view of the part of FIG. 1 showing the preferred embodiment of the invention, and

FIG. 3 is a longitudinal section through a part of a centrifugal pump showing an alternate structure of the invention.

Referring to the drawings, 10 designates a centrifugal type pump having a pump casing 12 within which is formed an impeller chamber 14 and a discharge 16 for the impeller chamber. The impeller chamber 14 is pro vided with an axial inlet 18 for admittance of fluid to be pumped. A rotating shaft 20 driven and supported by suitable means (not shown) is received in a bore 22 of the pump casing, one end of the shaft 20 extending through a bore 23 in the Wall of the impeller chamber and into the impeller chamber 14 to carry an impeller 24 in a commonly known manner.

Bore 22 forms a seal chamber including a rear chamber 26 and a forward chamber 28, each chamber having therein disposed a commonly known floating ring type sealing arrangement 30 and 32, respectively. The floating ring type seals 30 and 32 are of the type wherein there is no contact between the sealing elements and the shaft but where the seal is obtained by maintaining a close clearance between the shaft .and the sealing elements and providing for a limited flow of fluid through the clearance and along the shaft. Sealing arrangement 30 includes an elongated sleeve-like retainer 34 carrying a plurality of ring shaped sealing elements 36, each sealing element being formed by a washer 38 and a sealing ring 40. The sealing elements are adapted to cooperate with each other, with the inner periphery of the retainer, and with the shaft to permit a limited flow of fluid along the shaft through the clearances between the shaft and the sealing rings 40. Sealing arrangement 32 includes a relatively short sleeve-like sealing element retainer 42 carrying the same type sealing elements but fewer than carried by retainer 34.

The opposing ends of retainers 34 and 42 are spaced from each other to form a passage 44 into which injection fluid is conducted from a passage 46 formed between the periphery of bore 22 and retainer 34 and from conduit 48. The injection fluid introduced into conduit 48 is usually provided by-the boiler feed pump, however, it can be taken from any other suitable source of supply.

In order to provide for a constant flow of the injection fluid along the shaft and into the main impeller chamber 14 to prevent the fluid in the main impeller chamber 14 from flowing therefrom and along the shaft into the shaft housing, an auxiliary impeller 50 :and corresponding housing 52 are provided and mounted intermediate the wall of main impeller chamber 14 and retainer 42. Auxiliary impeller 50 is preferably mounted on shaft 20 and connected to impeller 24 to rotate therewith. The eye 54 of auxiliary impeller 50 is in communication with the interior of retainer 42, while the discharge of auxiliary impeller 50 is conducted through the auxiliary impeller housing 52, bore 23, passages 56 formed in the back shroud of impeller 24, and into the flow path of the fluid flowing from the eye of impeller 24 into main impeller chamber 14. It is to be noted that the location of passages 56 through the back shnoud of main impeller 24 is chosen in a low pressure area close to the inlet of the main impeller relative to the high pressure area at the discharge of the main impeller to provide for a relatively low dicharge pressure of the auxiliary impeller.

A commonly known sealing arrangement formed by back rings 58 is provided to prevent the flow of the high pressure discharge fluid of main impeller 24 into the flow path of the low pressure discharge fluid of the auxiliary impeller 50.

During operation of pump 10, injection water supplied by the boiler feed pump at lower temperature than the temperature of the Water being pumped through main impeller chamber 14 is conducted through conduit 48 and passage 46 to passage 44. As auxiliary impeller 50 is rotating with main impeller 24, an under pressure relative to the pressure of the injection water is created at the eye 54 of the auxiliary impeller 50, urging a portion of the injection water in passage 44 to flow through the clearance formed between the sealing elements in retainer 42 and the associated portion of shaft 20 into the the auxiliary impeller 50. The auxiliary impeller then pumps the injection water through the auxiliary impeller housing 52, bore 23, and passages 56 of main impeller 24 into the flow path of the water being pumped by main impeller 24. The other portion of the injection water flowing through passage 44 is conducted to flow through the clearance formed between the sealing elements in retainer 34 and the associated portion of the shaft 20 into a chamber 60 formed downstream of the flow of injection water through sealing arrangement 30 from where it is discharged in any suitable manner.

An alternate structure of the invention is shown in FIG. 3. In this structure the auxiliary impeller 50' and corresponding housing 52' are positioned between the sealing arrangements 30 and 32, auxiliary impeller 50' being mounted on shaft 20 in any suitable manner to rotate therewith. With this arrangement a portion of the injection water supplied through conduit 48 and passage 46 is drawn into the eye 54 of the rotating auxiliary impeller 50 and pumped thereby through the clearance formed between the sealing elements in retainer 42 and the associated portion of shaft 20 into bore 23, passages 56 of main impeller 24 and into the flow path of the water being pumped by main impeller 24. The other portion of the injection water flowing from conduit 48 and passage 46 is conducted to flow through the clearance formed between the sealing elements in retainer 34 and the associated portion of shaft 20 into chamber. 60 from where it is discharged in any suitable manner.

It will be understood that the invention is not intended to be limited to the specific construction or arrangement of parts shown, but that they may be Widely modified within the invention defined by the claims.

I claim:

1. A sealing and cooling device for a shaft of a rotary pump which is adapted for pumping fluid of relatively high temperature, said device comprising:

a casing having an impeller chamber and a seal chamber in communication with each other through an axial passage in a common wall between said chambers;

a rotatable shaft extending through said seal chamber and having an end extending with clearance through said axial passage into said impeller chamber;

a primary impeller carried by said shaft within said impeller chamber for rotation therein;

a plurality of axially spaced groups of annular seals surrounding said shaft in spaced relationship thereto within said seal chamber for permitting a restricted flow of fluid along said shaft intermediate said annular seals and said shaft;

means for introducing cooling fluid into said seal chamber intermediate said groups of annular seals such that portions of said cooling fluid flow continuously between each of said groups of annular seals and said shaft towards the opposing ends of said shaft; and

an auxiliary impeller upon said shaft within said seal chamber for rotation therein for directing the portion of said cooling fluid that flows towards said im peller chamber through said axial passage in said wall into said impeller chamber.

2. A cooling and sealing device according to claim 1 wherein said auxiliary impeller is disposed within said seal chamber adjacent said common wall between said seal chamber and said impeller chamber.

3. A cooling and sealing device according to claim 1 wherein said auxiliary impeller is disposed within said seal chamber intermediate said axially spaced groups of annular seals.

4. A cooling and sealing device according to claim 1 wherein said casing includes fluid carrying means adjacent the end of said rotatable shaft opposite to that carrying said primary impeller for carrying cooling fluid directed towards said former mentioned end of said rotatable shaft from said rotatable shaft.

References Cited by the Examiner UNITED STATES PATENTS 2,708,126 5/55 McLachl-an et al. 103111 3,128,713 4/64 Nichine 103-111 3,162,135 12/64 Nichols et al. 103-111 FOREIGN PATENTS 378,091 7/23 Germany.

592,327 2/ 34 Germany.

652,168 10/37 Germany.

881,400 11/62 Great Britain.

422, 1 15 1/ 47 Italy.

DONLEY J. STOCKING, Primary Examiner.

HENRY F. RADUAZO, Examiner. 

1. A SEALING AND COOLIONG DEVICE FOR A SHAFT OF A ROTARY PUMP WHICH IS ADAPTED FOR PUMPING FLUID OF RELATIVELY HIGH TEMPERATURE, SAID DEVICE COMPRISING: A CASING HAVING AN IMPELLER CHAMBER AND A SEAL CHAMBER IN COMMUNICATION WITH EACH OTHER THROUGH AN AXIAL PASSAGE INTO SAID IMPELLER CHAMBER; BERS; A ROTATABLE SHAFT EXTENDING THROUGH SAID SEAL CHAMBER AND HAVING AN END EXTENDING WITH CLEARANCE THROUGH SAID AXIAL PASSAGE INTO SAID IMPELLER CHAMBER; A PRIMARY IMPELLER CARRIED BY SAID SHAFT WITHIN SAID IMPELLER CHAMBER FOR ROTATION THEREIN; A PLURALITY OF AXIALLY SPACED GROUPS OF ANNULAR SEALS SURROUNDING SAID SHAFT IN SPACED RELATIONSHIP THERETO WITHIN SAID SEAL CHAMBER FOR PERMITTING A RESTRICTED FLOW OF FLUID ALONG SAID SHAFT INTERMEDIATE SAID ANNULAR SEALS AND SAID SHAFT; MEANS FOR INTRODUCING COOLING FLUID INTO SAID SEAL CHAMBER INTERMEDIATE SAID GROUPS OF ANNULAR SEALS SUCH THAT PORTIONS OF SAID COOLING FLUID FLOW CONTINUOUSLY BETWEEN EACH OF SAID GROUPS OF ANNULAR SEALS AND SAID SHAFT TOWARDS THE OPPOSING ENDS OF SAID SHAFT; AND AN AUXILIARY IMPELLER UPON SAID SHAFT WITHIN SAID SEAL CHAMBER FOR ROTATION THEREIN FOR DIRECTING THE PORTION OF SAID COOLING FLUID THAT FLOWS TOWARDS SAID IMPELLER CHAMBER THROUGH SAID AXIAL PASSAGE IN SAID WALL INTO SAID IMPELLER CHAMBER. 